Ranges of Sound & Applications of Ultrasound
Complete Class 10 Physics notes on sound frequency ranges and ultrasound applications.
Write the three ranges of Sounds.
Ranges of Sound: The sound is divided into three ranges according to their frequencies and audibility.
i) Infra Sonic Sound ii) Audible Frequency Range iii) Ultra Sonic Sound
i) Infra Sonic Sound
The sound having frequencies less than 20 Hz are regarded as infra sonic sound, these sounds are not audible for humans.
Sound produced by earthquakes, thunder, volcanoes are in Infrasonic range
ii) Audible Frequency Range
Those sounds lie in the audible region of humans are called in audible frequency range. These sounds have frequency from 20Hz to 20,000 Hz.
Vibrating sources that produce sound in the audible range of frequencies are drums, guitar strings, tuning fork, human vocal cords and diaphragms of loudspeakers.
iii) Ultra Sonic Sound
The sound having frequencies greater than 20000 Hz are regarded as ultra sonic sound, these sounds are not audible for humans.
An example of ultrasonic is a dog whistle that cannot be heard by humans, An example of ultrasonic is the detection of ships and objects underwater by bouncing a high frequency sound wave off their hulls.
Q.9 Describe important applications of Ultra sound techniques in industries and medicines.
Applications of Ultrasound: Ultrasounds, high-frequency sound waves can propagate along well-defined straight paths, Ultrasounds are used extensively in industries and for medical diagnostic (imaging) purposes.
1. Cleansing
Ultrasound is commonly used to clean many objects even in hard-to-reach places, including jewelry, dental and surgical instruments, and musical instruments. In this process, objects to be cleaned are placed in a cleaning solution, and ultrasonic waves are sent into the solution. Due to its high frequency, dust, grease, and contamination particles detached and dropped. The objects thus get thoroughly cleansed.
2. Quality control
Ultrasound has higher penetrating power due to its very high frequency. Thus, ultrasounds are also used to detect cracks, cavities, and flaws in metal and concrete blocks. These invisible cracks or cavities inside the blocks reduce the strength of the structure. Ultrasonic waves pass through the metal block, and detectors are used to detect the transmitted waves. If there is any defect, the ultrasound will be reflected, indicating the presence of the defect.
3. Sound navigation and ranging (SONAR)
SONAR is extensively used in marine applications. Due to their high frequencies, ultrasound waves can travel greater distances. In this method, the transmitter sends out ultrasound pulses and measures the time it takes for the pulses to reflect off a distant object and return to the source or transducer. The position of that object can be identified, and its movement can be tracked. This technique is used to measure the depth of sea beds, locate and track submarines at sea, and locate explosive mines below the surface of the water.
4. Echocardiography
Echocardiography is a painless and non-invasive medical imaging procedure. A transmitter sends out pulses of very high frequency. The transducer is positioned on the chest at specific locations and angles, the pulses move across the skin and other body tissues to the heart tissues, where the pulses bounce or echo of the heart structures. These pulses are then transmitted to a computer to create moving images of the heart walls and valves. The image produced is called an echocardiogram.
5. Ultrasonography
It is a technique that uses an instrument ultrasound scanner. This scanner uses high-frequency sound waves to obtain images of the internal organs of the human body and to examine the fetus during pregnancy. A sonologist visualize the organs of the patient, such as the liver, gall bladder, uterus, kidney, etc. It helps the doctor to identify abnormalities, such as stones in the gall bladder and kidney or tumors and abnormalities in different organs. In this technique, the sound waves penetrate the body and hit a boundary between tissues, e.g., between fluid and soft tissue, bone and soft tissue, and get reflected from an area where their tissue density changes.
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